/*******************************************************************************
 * Copyright (c) 2005, 2010 IBM Corporation and others. All rights reserved. This program and the
 * accompanying materials are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html Contributors: IBM Corporation - initial API and
 * implementation Jens Lukowski/Innoopract - initial renaming/restructuring
 *******************************************************************************/

package org.eclipse.wst.sse.ui.internal.derived;

import org.eclipse.jface.text.TextPresentation;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StyleRange;

import java.io.IOException;
import java.io.PushbackReader;
import java.io.Reader;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/*
 * Copied from org.eclipse.jdt.internal.ui.text.HTML2TextReader Modifications were made to add br/
 * tag and fix warnings
 */
/**
 * Reads the text contents from a reader of HTML contents and translates the tags or cut them out.
 */
public class HTML2TextReader extends SubstitutionTextReader {

  private static final String EMPTY_STRING = ""; //$NON-NLS-1$
  private static final Map fgEntityLookup;
  private static final Set fgTags;

  static {

    fgTags = new HashSet();
    fgTags.add("b"); //$NON-NLS-1$
    fgTags.add("br"); //$NON-NLS-1$
    fgTags.add("br/");//$NON-NLS-1$
    fgTags.add("h1"); //$NON-NLS-1$
    fgTags.add("h2"); //$NON-NLS-1$
    fgTags.add("h3"); //$NON-NLS-1$
    fgTags.add("h4"); //$NON-NLS-1$
    fgTags.add("h5"); //$NON-NLS-1$
    fgTags.add("h6"); //$NON-NLS-1$
    fgTags.add("hr"); //$NON-NLS-1$
    fgTags.add("p"); //$NON-NLS-1$
    fgTags.add("dl"); //$NON-NLS-1$
    fgTags.add("dt"); //$NON-NLS-1$
    fgTags.add("dd"); //$NON-NLS-1$
    fgTags.add("li"); //$NON-NLS-1$
    fgTags.add("ul"); //$NON-NLS-1$
    fgTags.add("pre"); //$NON-NLS-1$
    fgTags.add("html"); //$NON-NLS-1$
    fgTags.add("head"); //$NON-NLS-1$
    fgTags.add("body"); //$NON-NLS-1$
    fgTags.add("code"); //$NON-NLS-1$
    fgTags.add("font"); //$NON-NLS-1$
    fgTags.add("blockquote"); //$NON-NLS-1$
    fgTags.add("a"); //$NON-NLS-1$
    fgTags.add("tt"); //$NON-NLS-1$
    fgTags.add("tl"); //$NON-NLS-1$
    fgTags.add("em"); //$NON-NLS-1$
    fgTags.add("i"); //$NON-NLS-1$

    fgEntityLookup = new HashMap(7);
    fgEntityLookup.put("lt", "<"); //$NON-NLS-1$ //$NON-NLS-2$
    fgEntityLookup.put("gt", ">"); //$NON-NLS-1$ //$NON-NLS-2$
    fgEntityLookup.put("nbsp", " "); //$NON-NLS-1$ //$NON-NLS-2$
    fgEntityLookup.put("amp", "&"); //$NON-NLS-1$ //$NON-NLS-2$
    fgEntityLookup.put("circ", "^"); //$NON-NLS-1$ //$NON-NLS-2$
    fgEntityLookup.put("tilde", "~"); //$NON-NLS-2$ //$NON-NLS-1$
    fgEntityLookup.put("quot", "\""); //$NON-NLS-1$ //$NON-NLS-2$
  }

  private int fCounter = 0;
  private TextPresentation fTextPresentation;
  private int fBold = 0;
  private int fStartOffset = -1;
  private boolean fInParagraph = false;
  private boolean fIsPreformattedText = false;
  private boolean fIgnore = false;
  private boolean fHeaderDetected = false;

  /**
   * Transforms the html text from the reader to formatted text.
   * 
   * @param presentation If not <code>null</code>, formattings will be applied to the presentation.
   */
  public HTML2TextReader(Reader reader, TextPresentation presentation) {
    super(new PushbackReader(reader));
    fTextPresentation = presentation;
  }

  public int read() throws IOException {
    int c = super.read();
    if (c != -1)
      ++fCounter;
    return c;
  }

  protected void startBold() {
    if (fBold == 0)
      fStartOffset = fCounter;
    ++fBold;
  }

  protected void startPreformattedText() {
    fIsPreformattedText = true;
    setSkipWhitespace(false);
  }

  protected void stopPreformattedText() {
    fIsPreformattedText = false;
    setSkipWhitespace(true);
  }

  protected void stopBold() {
    --fBold;
    if (fBold == 0) {
      if (fTextPresentation != null) {
        fTextPresentation.addStyleRange(new StyleRange(fStartOffset, fCounter - fStartOffset, null,
            null, SWT.BOLD));
      }
      fStartOffset = -1;
    }
  }

  /*
   * @see org.eclipse.jdt.internal.ui.text.SubstitutionTextReader#computeSubstitution(int)
   */
  protected String computeSubstitution(int c) throws IOException {

    if (c == '<')
      return processHTMLTag();
    else if (fIgnore)
      return EMPTY_STRING;
    else if (c == '&')
      return processEntity();
    else if (fIsPreformattedText)
      return processPreformattedText(c);

    return null;
  }

  private String html2Text(String html) {

    if (html == null || html.length() == 0)
      return EMPTY_STRING;

    String tag = html;
    if ('/' == tag.charAt(0))
      tag = tag.substring(1);

    final int ws = tag.indexOf(' ');
    if (ws > 0) {
      tag = tag.substring(0, ws);
    }

    if ("head".equals(html) && !fHeaderDetected) { //$NON-NLS-1$
      fHeaderDetected = true;
      fIgnore = true;
      return EMPTY_STRING;
    }

    if ("/head".equals(html) && fHeaderDetected && fIgnore) { //$NON-NLS-1$
      fIgnore = false;
      return EMPTY_STRING;
    }

    if (fIgnore)
      return EMPTY_STRING;

    if (!fgTags.contains(tag))
      return '<' + html + '>';

    if ("pre".equals(html)) { //$NON-NLS-1$
      startPreformattedText();
      return EMPTY_STRING;
    }

    if ("/pre".equals(html)) { //$NON-NLS-1$
      stopPreformattedText();
      return EMPTY_STRING;
    }

    if (fIsPreformattedText)
      return EMPTY_STRING;

    if ("b".equals(html)) { //$NON-NLS-1$
      startBold();
      return EMPTY_STRING;
    }

    if ("h5".equals(html) || "dt".equals(html)) { //$NON-NLS-1$ //$NON-NLS-2$
      startBold();
      return EMPTY_STRING;
    }

    if ("dl".equals(html)) //$NON-NLS-1$
      return LINE_DELIM;

    if ("dd".equals(html)) //$NON-NLS-1$
      return "\t"; //$NON-NLS-1$

    if ("li".equals(html)) //$NON-NLS-1$
      return LINE_DELIM + "\t" + "- "; //$NON-NLS-1$ //$NON-NLS-2$

    if ("/b".equals(html)) { //$NON-NLS-1$
      stopBold();
      return EMPTY_STRING;
    }

    if ("p".equals(html)) { //$NON-NLS-1$
      fInParagraph = true;
      return LINE_DELIM;
    }

    if ("br".equals(html) || "br/".equals(html)) //$NON-NLS-1$ //$NON-NLS-2$
      return LINE_DELIM;

    if ("/p".equals(html)) { //$NON-NLS-1$
      boolean inParagraph = fInParagraph;
      fInParagraph = false;
      return inParagraph ? EMPTY_STRING : LINE_DELIM;
    }

    if ("/h5".equals(html) || "/dt".equals(html)) { //$NON-NLS-1$ //$NON-NLS-2$
      stopBold();
      return LINE_DELIM;
    }

    if ("/dd".equals(html)) //$NON-NLS-1$
      return LINE_DELIM;

    return EMPTY_STRING;
  }

  /*
   * A '<' has been read. Process a html tag
   */
  private String processHTMLTag() throws IOException {

    StringBuffer buf = new StringBuffer();
    int ch;
    do {

      ch = nextChar();

      while (ch != -1 && ch != '>') {
        buf.append(Character.toLowerCase((char) ch));
        ch = nextChar();
        if (ch == '"') {
          buf.append(Character.toLowerCase((char) ch));
          ch = nextChar();
          while (ch != -1 && ch != '"') {
            buf.append(Character.toLowerCase((char) ch));
            ch = nextChar();
          }
        }
        if (ch == '<') {
          unread(ch);
          return '<' + buf.toString();
        }
      }

      if (ch == -1)
        return null;

      int tagLen = buf.length();
      // needs special treatment for comments
      if ((tagLen >= 3 && "!--".equals(buf.substring(0, 3))) //$NON-NLS-1$
          && !(tagLen >= 5 && "--".equals(buf.substring(tagLen - 2)))) { //$NON-NLS-1$
        // unfinished comment
        buf.append(ch);
      } else {
        break;
      }
    } while (true);

    return html2Text(buf.toString());
  }

  private String processPreformattedText(int c) {
    if (c == '\r' || c == '\n')
      fCounter++;
    return null;
  }

  private void unread(int ch) throws IOException {
    ((PushbackReader) getReader()).unread(ch);
  }

  protected String entity2Text(String symbol) {
    if (symbol.length() > 1 && symbol.charAt(0) == '#') {
      int ch;
      try {
        if (symbol.charAt(1) == 'x') {
          ch = Integer.parseInt(symbol.substring(2), 16);
        } else {
          ch = Integer.parseInt(symbol.substring(1), 10);
        }
        return EMPTY_STRING + (char) ch;
      } catch (NumberFormatException e) {
        // log problem?
      }
    } else {
      String str = (String) fgEntityLookup.get(symbol);
      if (str != null) {
        return str;
      }
    }
    return "&" + symbol; // not found //$NON-NLS-1$
  }

  /*
   * A '&' has been read. Process a entity
   */
  private String processEntity() throws IOException {
    StringBuffer buf = new StringBuffer();
    int ch = nextChar();
    while (Character.isLetterOrDigit((char) ch) || ch == '#') {
      buf.append((char) ch);
      ch = nextChar();
    }

    if (ch == ';')
      return entity2Text(buf.toString());

    buf.insert(0, '&');
    if (ch != -1)
      buf.append((char) ch);
    return buf.toString();
  }
}
